Synthesis, Characterization, and Electrochemical Polymerization of Some 5,5-Fused Ring Terthiophene Tricarbonyl Manganese Complexes

Polythiophenes are of great interest for use in electronic materials due to their stability and favorable materials properties. Thiophene-based electronic materials provide an attractive alternative to conventional inorganic semiconductors. We have targeted hybrid materials that combine the versatility of transition metals with oligo- and polythiophenes. We report here terthiophenes in which the [c]-edge of the central thiophene is fused to a cyclopentadienyltricarbonylmanganese group. These thiapentalenyl complexes, [Mn{η⁵-SC₇H₃-1,3-R₂}(CO)₃], were prepared in moderate to good yields (50-80%) via ring closure of 1,2-diacylcymantrenes, [Mn{η⁵-1,2-C₅H₃(COR)₂}(CO)₃] (R = thienyl, 5-methylthienyl, 5-chlorothienyl, 5-bromothienyl) with Lawesson’s reagent. These complexes display high environmental stability and were characterized via spectroscopic methods as well as X-ray crystallography. Cyclic voltammetry shows that the unsubstituted terthiophene manganese complex is susceptible toward electrochemical polymerization, whereas the 5-methyl complex is not. X-ray photoelectron spectroscopy (XPS) confirmed the presence of manganese in the polymeric films and indicated a nearly identical bonding environment of manganese in the monomer and the films.